We cannot compare against origin/main branch because we build from sdist, not git.

--- tox-4.31.0/tox.toml.orig
+++ tox-4.31.0/tox.toml
@@ -41,12 +41,6 @@
       "--run-integration",
     ] },
   ],
-  [
-    "diff-cover",
-    "--compare-branch",
-    { replace = "env", name = "DIFF_AGAINST", default = "origin/main" },
-    "{work_dir}{/}coverage.{env_name}.xml",
-  ],
 ]
 
 [env.fix]
--- tox-4.31.0/pyproject.toml.orig
+++ tox-4.31.0/pyproject.toml
@@ -79,7 +79,6 @@
   "covdefaults>=2.3",
   "coverage>=7.10.7",
   "detect-test-pollution>=1.2",
-  "diff-cover>=9.7.1",
   "distlib>=0.4",
   "flaky>=3.8.1",
   "hatch-vcs>=0.5",